You can legitimately downgrade anytime; your Win 7 license is still valid (just not to be used at the same time at 10, since the Win 10 license is an upgrade li

You can legitimately downgrade anytime; your Win 7 license is still valid (just not to be used at the same time at 10, since the Win 10 license is an upgrade license). You can then re-upgrade to Windows 10 at any point, as long as it's on the same hardware (either doing a clean install using your Windows 7 key or no key, or doing another upgrade install). The 30 day window is the period of time where you can uninstall and revert to 7 from within Windows 10, without having to do a clean install of 7. Windows 10 removes files from the old version of Windows after 30 days.